It came into my mind that all of us has encountered some major events in our lives. Similarly, our Earth would have also gone through the events of same kind. Mass-extinction is one of those events. Have a Read!
Mass-extinction is also known as biotic crisis or extinction-level event. It is characterized by major loss of biodiversity. When the extinction rate of organisms outweighs the speciation rate of organisms, mass- extinction occurs. Till now, Earth has witnessed a total of five mass-extinction.
Reasons Behind Mass Extinction
1. Global cooling i.e. the time period of the ice age characterised by colder temperatures and glaciation.
2. Global warming i.e. rise in average temperature because of enormous emission of greenhouse gases.
3. Glaciation i.e. formation of glaciers or freezing of water bodies this, leading to destruction of aquatic life.
4. Fluctuations in Sea Level– In case of global warming the sea level rises while that in case of global cooling the sea level lowers down thus, adversely affecting the aquatic habitats.
5. Global Anoxia i.e. decrease in oxygen concentration in atmosphere may have caused extinction as organisms could not survive in absence of oxygen.
6. Volcanic Eruptions i.e. release of lava and a large amount of gases from a volcanic vent.
7. Entry of asteroid, comets, and Meteors on Earth.
8. Gamma Rays released from supernova event may be a reason for mass extinction as these rays can penetrate through cells and destroy them.
9. Disease– Genome to genome transmission of pathogenic diseases would have lead to extinction of a specific species. About 12% of species extinction has been caused by diseases.
A Brief of the Mass Extinctions (mya-million years ago )
This was all about the five mass extinctions. But, let me remind you that, we are moving towards the sixth mass extinction and the reason would be us, the Homo sapiens.
There is a immediate need of environmental conservation to avoid such events in future.
Earlier the mass extinctions were due to the natural changes but, for the sixth mass extinction, our fatal activities such as deforestation, environmental pollution, burning of fossil fuels and many more are enough to welcome another one in 240 to 540 years.